Fixed umask/permission issues. [TUS-2514]
Removed hardcoded school sql template location [TUS-2515]
Added Plugin module per [TUS-2481]

Conflicts:

	lib/TUSK/Core/Plugins.pm
Change content objective to textarea [TUS-2539]
Added missing IO::File module [TUS-2481]
Add MMTx constants to tusk.conf.explain

The configuration constants MMTxExecutable and MMTxIndexerTimeout are
optional, only needed if UMLS indexing is desired.
Merge branch 'opentusk-4_0_0-alpha7-br' into opentusk
Merge branch 'master' into installer6
Adding to INSTALL-sl (in progress)