added CCombinedLogFilter

CCombinedLogFilter allows you to attach multiple log filters to a log
route. Solves the 3rd problem described in issue #684 and first of #721.

Main reason for not changing filter property to filters is backwards
compatibility. yii 2 should allow multiple filters by design.
unit tests for criteria modification in beforeFind

some are currently failing due to issue #93
fixed relational beforeFind criteria modification

issue #93

this fix might break BC since possible criteria modifications that did
not apply in the past will apply now.
This fix is supposed to show up how a solution would look like, we need
to think about a solution that does not break existing applications.
added unit tests for beforeFind() and afterFind() on empty result

when a query does not return results beforeFind() is called for all
eager relations even when main query did not return a result.
This is a behavior change, things are all consistent now.
afterFind() should of course never get called then.
added UPGRADE note for beforeFind() relational criteria

also fixed UPGRADE file whitespace issues for better readability
Merge branch 'master' into 93-relational-beforefind-criteria-modification

* master: (180 commits)
  Updated changelog with last-modified date change.
  Changed the CHttpCacheFilter to use RFC 1123 complaint dates when returning the last-modified header.
  tabs...
  gii: better default validation "length" rule for fixed-point / floating-point field type (MYSQL)
  fixes #1319
  updated comment in CHttpSession
  Update framework/YiiBase.php
  Update docs/guide/database.arr.txt
  New unit test for enhanced $gCProbability s/getters in CHttpSession #486. Fixed those methods to process corner cases properly. Initial $gCProbability is now double(1.0), was > 1.0 before.
  Bug #112: MSSQL: database abstraction layer now uses native transaction support of the SQLSRV driver.
  Forgot about spaces in comments creating procedure call. [ci skip]
  Better comments testing method name.
  Forgot about local MSSQL database settings.
  MSSQL unit testing SQL file reformatted and decorated. MSSQL testing class improved. Added unit tests for column comments retrieving.
  Removed old message.
  Update docs/guide/topics.i18n.txt
  Update docs/guide/topics.i18n.txt
  Requirements checker: russian (ru_RU) messages.
  Minor fixes and refinements to the MSSQL unit tests.
  better fix for issues #124
  ...

Conflicts:
	UPGRADE
small enhancements to UPGRADE instructions
added CHANGELOG line
Merge pull request #1102 from cebe/93-relational-beforefind-criteria-modification

fixed relational beforeFind criteria modification #93
reverted pull request #1325

fix did not address the real problem
Merge branch '684-combined-logfilter' of https://github.com/cebe/yii into cebe-684-combined-logfilter

* '684-combined-logfilter' of https://github.com/cebe/yii:
  added CCombinedLogFilter

Conflicts:
	framework/logging/CLogRoute.php
renamed CCombinedLogFilter to CChainedLogFilter

added changelog line
Merge pull request #1005 branch 'cebe-684-combined-logfilter'

* cebe-684-combined-logfilter:
  renamed CCombinedLogFilter to CChainedLogFilter
  added CCombinedLogFilter