Added AbstractIndexReaderWarmer plugin

This plugin allows the warming of indexreaders created from
indexwriters.  It's useful for initializing fieldcache values before the
first query requests them for things like faceting or sorting.
Assigning indexreaderwarmer for RamWriter

The indexreaderwarmer was not being assigned in CreateRamWriter.
Renamed IndexWarmers to IndexReaderWarmers
Renamed IndexWarmers to IndexReaderWarmers

In WorkContext.
Use the right convention
Fixing occasionally failing tests of RavenDB_406. It's better to use the 'comparision lessOrEqual' instead of 'less' because sometimes can happen that compared time values are the same while item needs to be checked. Probably it can happen only on localhost but now we are sure we don't serve an old value.
Fixing typo: aggresive => aggressive
Adding unit tests for RavenDB-1251
Fix RavenDB-1251 for sorting custom range types

Custom range types should use "_Range" field for sorting
Minor cleanup
* issue RavenDB-1260 Index type casing in Map
* changed class names for issue 1259, 1261 unit tests
Merge branch '2.5' of https://github.com/myarichuk/ravendb into 2.5
Merge branch '2.5' of https://github.com/mj1856/ravendb into 2.5
Merge branch 'aggresive-cache-convention-fix-2.5' of https://github.com/arekais/ravendb into 2.5
Merge branch 'master' of https://github.com/bczifra/ravendb into 2.5
DynamicField not analyzed shouldn't analyze
Making sure that we are comparing doubles properly
Adding passing test