Add simple PR tests

[gonX]

Some ideas:

JSON Key	Check
Name	^.{2,}$ (2 characters or more)
Description	same as Name
Owner	^[^\s]+$
SupportedDriverVersion	Must be lower than newest release, and have all 4 version subvalues (e.g. 0.6.4.0, not 0.6.4)
PluginVersion	^\d+(\.\d+){1,2}$ or less strict
*Url	must be curl'able (or similar)
CompressionFormat	Whatever we support, zip only for now? Can skip this check
LicenseIdentifier	Ideally, something from a predermined list, but otherwise same check as Owner

Already covered in tests:

• SHA256
• DownloadUrl

[gonX]

Oops, we already have some tests:
https://github.com/OpenTabletDriver/Plugin-Repository/blob/acc79dccf8325459e2e3f6b2be8bd4c197c222ed/validate.sh

Looks like SHA256 (and DownloadUrl) are the only ones getting tested there, as well as checking whether the file is parseable at all.

[gonX]

Updated OP to address issues fixed in #89

[gonX]

Also need to test for path as seen in #90 and #126. Fixed in #127

[Kuuuube]

Path test added in #127