new bitmask converter tool + misc changes

a new bitmask to flags converter tool has been added:
- a gear icon will appear next to those bitmask values which are
different from the TDB value
- clicking on this icon will bring up the tool itself in a window, in
which you can select the desired flags and unselect the undesired ones
- saving your changes will make the new value appear instead the
previous one and the original value will be also visible in brackets
next to it

misc usage related fixes and changes:
- total number of queries can be started at the same time is now limited
to 20 (via multiple queries function)
- now it's possible to define ports in php config file
- refreshing the query using F5 doesn't reset the scroll position of the
output anymore
- opening any windows (multi/sql/bitmask) will now bring up a shadow
effect behind the window, disabling mouse clicks anywhere else
- clicking next to a window will now close it (and in case of the
bitmask window, it will save the changes)