Merge branch 'feature/partial_fix' into develop
Merge branch 'develop'

Conflicts:
	structr-core/src/main/java/org/structr/core/EntityContext.java
added owner property to ui view
some progress on partial rendering, but creating partials
for markup elements is disabled for now, needs rework
some minor bug fixes
added specific HTML attributes
fixed NPE in registration endpoint
Merge branch 'develop'
disabled login with empty string as password
set session id in case of successful registration
new text function 'abbr(str,maxlen)' to shorten text to maxlen,
does not cut words
abbreviate text only if longer than maxlen
First attempt to optimize transaction handling and general write performance of structr, very WIP.
Work in progress.
Work in progress.
Modified validation mechanism, still work in progress.
Work in progress.
First working version of new transaction handling.
Modified SynchronizationController to support changes in EntityContext and TransactionCommand, added some performance logging, still wip.
Some additional performance tweaks.
More performance-related changes.