Kintree

SnapEDA
* Separated handling of symbol and footprint images
* Added referer in download link (per request from SnapEDA team)

GUI
* Fixed call to subcategories with function keys

* Added support for InvenTree global categories parameter templates: useful for custom parts
* Improvements to SnapEDA search: handles multiple results and use MPN instead of original user input

Major Updates

* Added SnapEDA API methods to check availability of symbol and/or footprint and potentially download them
* Added button that let user check if symbol and fooprint are available on SnapEDA.com (KiCad Libraries window)
* Added preview of symbol and footprint and download button to open a new browser tab directed to the download page

Minor Updates

* Cleaned-up KiCad V5 symbol templates to make them more "compatible" with KLC ruleset
* Cleaned-up part creation flow
* Fixed 7 (thanks watarat for my first bug report!)
* Fixed :beetle: where user could add the separator value to the list of most-used library choices (both symbol and footprint)

Added new features!

Global
- Now saving part into main category if subcategory does not exist in InvenTree
- Added "Add Custom" menu option to add parts to KiCad and InvenTree bypassing Digi-Key API
- Added timeout to InvenTree server connect and Digi-Key API search

GUI
- Now informing user of part creation progress with GUI window
- Show form prefilled with part API search results and allow user edits
- Switched to YAML file format for part search API results
- Added timestamp to API data for caching management

> Note: Although all tested, some new features may still feature bugs :beetle: (hence the beta release)

* Improved test code coverage
* Code refactoring and clean-up
* Continuous integration using Travis CI