Apply #418: MySQL compatibility: support for ALTER TABLE tbl_name MODIFY [COLUMN] col_name column_definition, patch from Ville Koskela.

suggestion from markaddleman@gmail.com

There was a possibility that the .lock.db file was not deleted when the database was closed, which could slow down opening the database.

Optimize IN(...) queries: there was a bug in version 1.3.170 if the type of the left hand side didn't match the type of the right hand side.

When using trace level 4 (SLF4J) in the server mode, a directory "trace.db" and an empty file was created on the client side. This is no longer made.

Patch by lukas.eder@gmail.com

Optimize IN(...) queries: there was a bug in version 1.3.170 for comparison of the type "X IN(NULL, NULL)". Fixed.

Timestamps with timezone that were passed as a string were not always converted correctly. For example "2012-11-06T23:00:00.000Z" was converted to "2012-11-06" instead of to "2012-11-07" in the timezone CET.

Patch from Andrew Gaul argaul@gmail.com
Fixes issue 406.

Patch from Andrew Gaul argaul@gmail.com
Fixes issue 401.

MVStore: store the file header also at the end of each chunk, which means even less write operations

MVStore: unified exception handling; the version is included in the messages. Old data is now retained for 45 seconds by default.