Merge pull request #268 from bastih/master

Alleviate major grievance - casts in AbstractTable no longer fail silen...
Add LIKE and IN expression

Like Expression for strings comparison with regex syntax.
In Expression: takes an array of selected value type and checks for fields that match one of these values.
Merge pull request #265 from kateyy/feature/Like_In_Expressions

Add Like and In Expression
Implement concurrent facilities for Store

* Introduce ConcurrentUnorderedDictionary, a concurrent insertion safe
  dictionary.

* Introduce ConcurrentFixedLenghtVector, a storage structure that may be
  grown safely by multiple threads

* Add AbstractTable::copy_structure with callbacks for backing
  structures, allowing Store to use concurrent structures

* Add AbstractFixedLengthVector so that ConcurrentUnorderedDictionary
  may safely fill in where FixedLengthVector was used
Merge pull request #258 from bastih/feature/concurrent_delta

Concurrent delta