Fix PVR GetMinSchemaVersion() signature

So it doesn't just hide, but also overrides the CDatabase version

May fix lurking database upgrade issue.

Fixes Coverity CID 1194377:
bad_override: Method PVR::CPVRDatabase::GetMinSchemaVersion hides but
does not override CDatabase::GetMinSchemaVersion because some type
qualifiers do not match.
Return password from input dialog

When a password was being asked for, it would be collected, but due to a
missing break the code fellthrough into the default case, and returned
an emptyString.

Fixes Coverity CID 1126027
Merge pull request #4462 from cg110/CoverityFixes2

A couple more bugs fixes from Coverity