Merge tag '0.27' into develop

Integrated with Travis CI
Fixed duplicate column detection in insert and update
Removed obsolete tags from value types
Moved operator and parameter templates out of value classes, added member template

These templates are nicer when used.
Minor code cleanup
Applied new member_t to remaining places
An alias for creating a new statement type
Meta function for accessing the lhs and rhs of an expression
Added a few comments for better orientation
Sprinkled in a few const qualifiers
Added include for MSVC to understand and and or
Added derived_statement_t alias
Minor cleanup
Removed stray sqlpp namespace qualifiers

The usage was very inconsistent. Also, I just saw that the current VC++
cannot deal with qualifiers in combination with template aliases
Cleanup in generated code
Added operators to the 'like' member_t
Added missing include
Minor fix (less error spew for 'like')
Added a few examples
Added a few bad examples (commented)