Fixes#3199.
Ensures that the model package compiler passes schema validation for
kmp.json. Three problems were corrected:
1. `followKeyboardVersion` is a source-only property; it should not be
in deployable kmp.json.
2. `copyLocation` should have been a number not a string (in XML
everything is a string... but JSON has more control here)
3. `fileType` is a source-only property; it also should not be in
deployable kmp.json.
I have checked that the resulting files validate against the package
kmp.json schema version 1.1.0 defined at
https://github.com/keymanapp/api.keyman.com/blob/master/schemas/package/1.1.0/package.json.
None of these fixes should impact the use of these packages in target
apps. `followKeyboardVersion` and `fileType` are used only in the source
at package development time, and `copyLocation` is unused (and should be
eliminated from Keyman altogether in the future).
