Various contributions to Stellar Explorer

The post title is "Various contributions to Stellar Explorer", but I have done contributions to other projects in the meantime too. They are linked below, I can't change the post title though.

For this SBC I went through the list of projects the SDF suggested contributing to. Stellar Explorer (https://steexp.com) interested me the most and in the last month I have dived deep into the project and made an effort to provide valuable contributions to it.

I have resolved the following issues, my PRs were all merged by the maintainer. All the work I did were existing issues labelled with "Help wanted" by the maintainer.

• I implemented a data export: https://github.com/chatch/stellarexplorer/issues/67.
  This enables users to download data and process it offline via a tool of their choice.

• I implemented a loading screen: https://github.com/chatch/stellarexplorer/issues/72.
  Before this it was unclear to users that the app is starting up and not just failed silently.

• I fixed a nasty bug in the pagination mechanism: https://github.com/chatch/stellarexplorer/issues/65.

• I implemented a way to flexibly switch the backend to a horizon instance of the users preference: https://github.com/chatch/stellarexplorer/pull/91.
  This enables people to use Stellar Explorer with e.g. a locally running horizon instance or one which has e.g. a better network reachability (this is relevant for example in China).

• I implemented a way to filter the pagination results returned by Horizon: https://github.com/chatch/stellarexplorer/pull/93.
  This is used in Stellar Explorer now to provide the capability to filter tables in the UI for a criteria.
  While implementing this I found a bug in js-stellar-sdk and provided a PR which fixed it: https://github.com/stellar/js-stellar-sdk/pull/193 (has been merged).

• I investigated a bug and found out the issue could be closed: https://github.com/chatch/stellarexplorer/issues/29.

• Distributed over these PRs I have done various refactorings, code improvements, and added tests and documentation.

I quite enjoyed contributing these things and had another look at the projects which the SDF had listed. As a result I have contributed these things:

Stellar Scala SDK:

• I implemented cursors and order modifiers (asc/desc): https://github.com/Synesso/scala-stellar-sdk/pull/30.

• I implemented a part of the operations API: https://github.com/Synesso/scala-stellar-sdk/pull/31.

• I found out one issue could be closed: https://github.com/Synesso/scala-stellar-sdk/issues/10.

• I implemented a part of the effects API: https://github.com/Synesso/scala-stellar-sdk/pull/32.

Stellar PHP SDK:

• I added documentation on how to install the SDK, a user had created an issue because it was unclear: https://github.com/zulucrypto/stellar-api/pull/23.

I also created PRs on existing issues for some other projects which the SDF had listed. Unfortunately the maintainers have not reacted at the time of this submission (I
created the issues ~10 days ago and had pinged them again without success):

• stellarterm:
  • Improvements to the CI: https://github.com/stellarterm/stellarterm/pull/295.
  • Bug fix for an issue which was created by people from the SDF: https://github.com/stellarterm/stellarterm/pull/294.

• stargazer:
  • I set up a CI environment (travis): https://github.com/future-tense/stargazer/pull/89.