FlxTilemap ignores last tiles if startingIndex is > 0

_tileObjects now takes startingIndex into account.

Fixed FlixelCommunity/flixel#55, AdamAtomic/flixel#176
overlapProcessed isn't properly cleared in FlxQuadTree

_notifyCallback is now only called is _processingCallback returned true that iteration.

Fixed FlixelCommunity/flixel#29, AdamAtomic/flixel#203
FlxTilemap not clearing variables before loadMap

I've added a clearTilemap function that properly resets everything before every call to loadMap. I also set visible and active to false in the constructor, so that flixel doesn't attempt to draw a tilemap before it's been loaded.

Fixed FlixelCommunity/flixel#46, AdamAtomic/flixel#185
Fixed FlixelCommunity/flixel#34, AdamAtomic/flixel#197
Add `FlxGroup::revive()`

The FlxGroup will now revive itself, and then all its members.

This is to compliment `FlxGroup::kill()`.
Fix minor typos in `FlxGroup::revive()`

It's a minor typo, but with major consequences!

If left unchecked, this bug would revive already existing objects,
leading to several Science Fiction worthy paradoxes.

Also fixed a tiny spelling typo in the ASDoc.
Only revive `FlxGroup` objects if they are `alive`

After some discussion on GitHub
https://github.com/FlixelCommunity/flixel/pull/110/files#r1831839
it seems the more logical to check if an object is `alive`,
rather than check if it `exists` when reviving it.
Fix `FlxCamera` jitters when following a target

Resolves the following issue:
 * https://github.com/FlixelCommunity/flixel/issues/5 - https://github.com/AdamAtomic/flixel/issues/227

Fix provided by [Krix](https://github.com/krix)
Rename `FlxSprite::simpleRender` to `isSimpleRender`

Will also avoid an error if the `target` object is not a `FlxSprite`.
no need to fill a camera twice if not blending alpha
Change `FlxSprite::isSimpleRender` into a function

Also does some minor cleanup of making sure brace placement matches the rest of the code, and removes one unecessary comment.
Fix issue #37 FlxTilemap.overlapsWithCallback calls callback when no overlapping.

The overlapping check performed for tiles with allowCollision = false ignored the object widht/height, so the tile callback would fire even when the Object was placed close to, but not overlapping, the tile.
Fix regression introduced by camera fix.

Pull request 119 https://github.com/FlixelCommunity/flixel/pull/119 fixed issue #50, but it introduced a new bug related to the camera bounds. This commit reverts all changes made by pull request 119, fixing the introduced FlxCamera problems.
Merge pull request #171 from Dovyski/fix_issue_165

Fix regression introduced by camera fix.
Merge pull request #99 from moly/fix_issue_176

FlxTilemap ignores last tiles if startingIndex is > 0
Merge pull request #100 from moly/fix_issue_203

overlapProcessed isn't properly cleared in FlxQuadTree
Merge pull request #110 from IQAndreas/fix-flxgroup-kill

Add `FlxGroup::revive()`
Merge pull request #166 from Dovyski/fix_issue_37

Fix issue #37 FlxTilemap.overlapsWithCallback calls callback when no overlapping
Fix FlxSprite.drawLine() incorrect behavior when full transparency set in color

Fixes #170.
Merge pull request #173 from Dovyski/fix_issue_170

Fix FlxSprite.drawLine() incorrect behavior when full transparency set in color
Prevent setting a FlxSprite to an invalid frame

Fixes https://github.com/FlixelCommunity/flixel/issues/13

Prevents an "out of range" frame number from being set either by an
animation, or by manually setting the `frame` property.

Adds new getter/setter `numFrames` where user can manually specify how
many frames an animation has (in case some frame are empty).

To go hand in hand with this is the read-only property `maxFrames` which
calculates how many frames can fit on that sprite sheet. NOTE: it rounds
up, so sprites may "hang off the edge" if the sheet is the wrong
dimensions. This may be fixed in the future depending on how other
applications handle "overhanging frames".