Various bugfixes to spellbook screen.

Arcane and Divine tabs did nothing for a multiclass character.  They're
slightly functional now, with the possibly unwanted side effect of letting
spells per level count separately for arcane versus divine.  Multiclassing
still needs a lot of work; spellcaster code checks player level, not class
level, so a wizard 1 / cleric 1 has the spellcasting of a wizard 2 + cleric 2.

Disallow right-clicking to reduce the number of spells prepared below 0.

Tabs and spells per level were as wide as the dialog, which meant they
overlapped (and prevented the use of) the alphabetized spell list.

Charges display was too narrow, which meant it didn't display for some spells
(like a wizard's Summon Monster I).

Clicking on the alphabetized spell list caused an error, because fct was
unimplemented.  I implemented a simple fct to behave the same as clicking on a
spell's icon.  More cleanup would be good; it would be nice if the
alphabetical spell list and by-level spell list weren't in such different
formats, so code could be more easily reused.
Fixes for Animal Empathy and Diplomacy.

Using the skill on an invalid target no longer wastes a turn.

Befriending a target no longer resets the AI of every creature on the level.

Slightly more useful messages.

Using Diplomacy on yourself made everyone your friend.  Although very amusing,
this is now fixed.  Animal Empathy may need a similar fix if something like
wild shape ever changes the player's type.
Clean up character tooltips.

Delete tab characters in tooltips.  These were showing up as blocks because
the font didn't recognize them.

Show fractional CRs as fractions (like "1/6") instead of decimals ("0.1666667").
Merge pull request #141 from joshkel/bugfixes

Bugfixes
update documentation
narrow down log display
fix bard spells & give spellbook to paladins and rangers
fix brainfart in docs (thanks Castler)
fix mouse problems (thanks Castler!)
spell level tabs in spellbook!
arcane mount spell fix
fix club and quarterstaff
fix stat increasing dialog
fix water elemental desc
fix fireball and light spells
fix spellbook refresh and make it scale again
comment out lvl 10 cheevo since it doesn't work
add range to exotic ranged weapons' desc
add tooltips to store interface
no more spellbooks for NPCs; give raven placeholder text