Fix & improve Attribute class

Fixed a problem with the copy constructor which was causing crashes
(fixes #661 and #664)
Added copy and move assignment operator
Added move constructor
Using uint8_t pointer for value instead of void so that we can use
pointer arithmetic to increase int attributes.
code cleanup
New monster pack
missing files
missing spells
missing files
final edition
deleted repeated files
fix experience
small fix
Optimizations
Fix ConditionDamage::updateCondition bug

This commit fixes issue #618
Fix sharpshooter spell

Fixes issue #354 and #379
Fix deadlock
Merge pull request #669 from nawyrus/master

New monster pack
Use reference counting for DBResult
Avoid heap allocation if player is offline
Update pugixml to version 1.4
Fixed indentation in new monsters files
Small fix