Corrections and Additions before merging.

[BUGFIX] Fixed #15
[BUGFIX] Fixed mostly #16
[BUGFIX] You can add Min and Max prices with negative numbers.
[BUGFIX] Disconnecting and reconnecting in a store will not remove the player's pager (What if 39 players disconnects inside a store and we store the pager even if they are not online? memory waste). I added two listeners for this.

-- Code related
[DEPRECATION] Removed all getTypeID() and replaced with ItemStack.getType(), according to Material modification in our lists.
[CODE] isForbidden and isTool now stores the Material enum instead of the pure id. (hint: Material already has a method called maxDurability. I marked as deprecated RSUtils.maxDur because is strongly useless, and isTool is useless too because we can say "is a tool" watching at its durability).
[CODE] Modified all stolenToclaim related methods to a more human comprensible toClaim() (we use it not only for stolen item right?).
[POSITIONING] Repositioned methods in RealShopping according to their conceptual areas (I know, I won't do that again I promise. It was too late).
[DOCUMENTATION] Added documentation for some methods.