Allow resource overrides for main UI.

[splatch]

This commit solves #551 where user requested a way to customize UI colors or logo.
Now, with OSGi bundle fragment, just like in OH 2.5 it is possible to put new/additional resources.
Just create an OSGi fragment with patch/app/index.html, patch/app/css/xyz.css.
After reload of system, if fragment is matched properly, patched index will take a rule over default one.

[ghys]

LGTM

[digitaldan]

Hey @splatch, i'm not familiar with bundle fragments, do you have an example somewhere that targets either the main ui or paper ui? Just curious how you target a fragment project in eclipse (i assume thats where you start) to work with a specific OH bundle.

[splatch]

@digitaldan quickest tips I can give you - make sure that module you build have a Fragment-Host header pointing to openhab main ui bundle (org.openhab.ui). Inside IDE/maven module create a src/main/resources/patch/app/index.html, it will then override a main entry point used for browser. The whole trick in this PR is manipulation of bundle classpath so it first looks at patch/ and then own resources/classes. Since compiled OH main ui is packaged inside app/ you need to make all overrides through src/main/resources/patch/app.

I know there are million of things webpack/browser is doing so customization capabilities are fairly limited. You should be starting from copying of index.html used by UI version you have. With this you can start injecting an extra css and maybe other stuff (haven't tested it to be fair) just like you would do with standard HTML stuff ie. <link href="css/extra.css" rel="stylesheet">. Just remember to place it in src/main/resources/patch/app/css/.