changed sql string to be a constant

Signed-off-by: Markus Andree <me@hapm.de>
added VotaPlugin.findMarks() method (refs #11 @20m)

Signed-off-by: Markus Andree <me@hapm.de>
removed unneeded imports

Signed-off-by: Markus Andree <me@hapm.de>
added default constructor to PlayerMarks to make ebean happy

Signed-off-by: Markus Andree <me@hapm.de>
added first implementation for /top10 command (refs #11 @20m)

Signed-off-by: Markus Andree <me@hapm.de>