[INTERNAL] ODataMetaModel add error handling

NOTE: Change based on https://git.wdf.sap.corp:8080/#/c/730912/

Test:
**Metadata failed:
http://localhost:8080/testsuite/explored.html?realOData=true#/sample/sap.ui.core.sample.ViewTemplate.scenario/preview
+ cancel basic authentication popup
**Metadata failed:
use fiddler with autoresponder for annotations xHR returning 404

PS1: PP Sven,Knut; errorhandling for metadata only, annotations
outstanding
PS2: PP Thomas, Knut: annotations
PS3: trailing whitespaces
PS4: Comments TCH
PS5: JSDoc + UnitTests regarding empty metadata, dataservices, schema
and entity types
PS6: Comments Sven
PS7: rebased
PS8: rebased
PS9: Comments Patric, Jens H.

Change-Id: Ie37ed41d6da8be19ac3c16f7db32af63db042074
JIRA:FLPUISERVICES2014-1053
[FIX] ThingInspector Overlay contrast

Change-Id: I3d79830af539e901cc1200aeaa0b3ee519d7fec4
CSS: 0120031469 0000695384 2014
Merge "[INTERNAL] ODataMetaModel add error handling"
Merge "[FIX] ThingInspector Overlay contrast"