Add CMake option SOCI_STATIC (default=ON)

Close #80
Export SOCI_CORE_TARGET_STATIC  to parent scope

Rename left over old name -static to _static
Set SOCI_STATIC=OFF for travis-ci

[ci skip]
Try make -j on travis-ci

Try to determine number of available threads
Release PGresult when an exception is thrown

Fix involves:
* Call PQclear in throw_postgresql_soci_error
* Change throw_postgresql_soci_error to take pointer by reference to
effectively reset result
* PostgreSQL tests pass
* Close #86
Rename res to result for consistency.

(std::unique_ptr would be bless for correct and simple RAII across SOCI)
Add Visual C++ 11.0 to pre-defined compilers

Close #87

[ci skip]
Fix OUT direction of IN/OUT procedure parameter

Solve issue #81
Bring back convert_from_base() for the input ("use") parameters (removed
as unnecessary in SHA: 22e740a6)
Add comments with clarification why these conversion is necessary, by
design
Split Oracle's test7 into three separate tests
Tests pass for Oracle XE 10g.
Remove auto keyword left over by accident
Merge pull request #88 from mloskot/issue-81

Fix OUT direction of IN/OUT procedure parameter
Add TODO comment for commented convert_to_base

To review changes submitted in SHA:
c166625a28f7c907318134f625ff5acea7d9a1f8 and currently disabled. Likely,
to be removed.
Make loggged test names more consistent

[ci skip]
Update version to 3.2.0
Update requirements note

[ci skip]
Update tests of query_transformation feature #66

Test effects of transformation on prepared statements.
Test C++11 lambda as query transformation function.
Test simple no-op transformation.
Untabify
Disable CTest submissions to CDash

Tests result submission to cdash.org is still configured in
CTestConfig.cmake file, but at the moment we don't use it. In future, we
may want to re-enable it to let users help us testing, but then we will
have to review and test the submission actually works.

[ci skip]
Change version to 3.2.0 as current release

List DB2 and Firebird as supported database systems

[ci skip]
Prepare for documentation of release 3.2.0

Introduce versioned documentation copied to folders, one per each
release.
Documentation for previous releases will be copied from source packages
or release branches.

[ci skip]
Remove target="_blank" from doc.html link

[ci skip]
Split basics.html into two separate pages

Rename basics.html to connections.html
Add queries.html with simple queries copied from connections.html

[ci skip]