common: Add goal definitions

Until now, validation checking was performed by a comparison with numbers
1 and 9. This commit defines values of minimal and maximal goal and validating
function for goal checking simplification.

Change-Id: I9bb1c764246ee92798440e9af90eba438cf51c01
common: Refactor serialization methods macro

This commit makes LIZARDFS_DEFINE_SERIALIZE_METHODS macro more intuitive to use
including updates in code that uses it.

Change-Id: Ic26d100fe73bbac325dc5f91e9a9dd18bd67ff87