Support casts to boolean and double in Access.

Fixes failing test AggregateTest.testGroupBy.
Merge pull request #681 from slick/tmp/access-casts

Support casts to boolean and double in Access.
Add documentation for `into` method
Merge pull request #687 from slick/tmp/into-docs

Add documentation for `into` method
Emulate empty join conditions where needed.

Appending the dummy condition "on 1=1" works almost everywhere, except
in Access, where the condition has to reference columns from both sides
of the join, so we have to thread the dummy "1" values through the
sub-queries.

Fixes Typesafe support ticket 3140.
Test in JoinTest.testNoJoinCondition.
Fixed issue #554 (ZIP joins)
Merge pull request #708 from Radsaggi/tmp/issue554

Fixed issue #554 (ZIP joins)
Fixed issue #698 (MappedColumnType broken for Char)
Add test for broken mapping to Char
Merge pull request #712 from Radsaggi/tmp/issue698

Fixed issue #698 (MappedColumnType broken for Char)
Merge pull request #700 from slick/tmp/support-3140

Emulate empty join conditions where needed.
Prevent "no-symbol does not have an owner" when using MappedTo.

Fixes issue #590. Test in RelationalMapperTest.mappedToMacroCompilerBug
(compile-time only; the test is not executed)