Micro AIs: use new fight_on_without_leader= key as needed

So that the scenarios with leaderless AI sides work.
Micro AIs: avoid code duplication between eval and exec functions
fix minor bug in get_healing_phase
AOI S6: correct user_team_name for side 2 to Undead
Merge pull request #143 from Kevin-Xi/bugfix

fix minor bug in get_healing_phase
NR S7a: fixed typo in a comment
NR S10a: fixed typo in comment
THoT S1: improved a sentence
THoT S2: added mission period
THoT S12: fixed a typo and a missing word

Then -> Then
We will able -> We will be able
UtBS S6a: fixed typo in comment
fix bugs and add comments on simple_move_and_targeting_phase

fix bugs and add comments on simple_move_and_targeting_phase

fix bugs and add comments on simple_move_and_targeting_phase
Merge pull request #144 from Kevin-Xi/bugfix

fix bugs and add comments on simple_move_and_targeting_phase
Messenger Micro AI: minor code simplification
Micro AIs: avoid using table.remove

It’s slow.  The inverse logic using table.insert is much faster,
especially for large tables.  Only kept table.remove in a couple places
where it doesn’t matter.
Micro AIs: avoid using formula= in SUFs

It’s slow for finding units with moves or attacks left.  The
alternative method of getting all units and then looping over the table
with a condition is much faster.
Fix a typo

I had actually introduced this typo intentionally for testing purposes
and then forgotten to remove it.  :-P
Use 'faction' and 'gender' attributes to provide default values in MP Create.

Before this, 'faction' and 'gender' were not used if 'force_lock_settings'
wasn't set to 'yes'. This resulted in inconsistent behaviour between the
mentioned two attributes and 'type' attribute. When 'type' was set, the relevant
leader was always selected by default.

This partially fixes bugs #21753 and #20562. To properly address them, it might
be needed to add 'faction_lock', 'type_lock' and 'gender_lock' attributes so
that UMC authors would have a way to actually lock these selections without
using 'force_lock_settings' if they don't want to.