Parse files one at a time in EnemyGroupManager

Loading enemy files to read enemygroup information was done by
essentially concatenating all of the enemy files together. This broke
the ability to overwrite that data via the same file across mods.

Instead, we now get a list of all the enemy files and parse each one
individually.
Implement more consistent file parsing method

Closes #1040

Now by default, all mod files will overwrite eachother. For files that
were automatically concatenated before, they can still be concatenated
by making the first line of all but the first file "APPEND". For
example, we can combine the credits for the engine, fantasycore, and
alpha_demo by adding "APPEND" to the top of the credits cutscene files
in fantasycore and alpha_demo.
Remove usage of Quest index

Instead of reading quests/index.txt to find out which quests files to
load, we now just grab all the files in quests/. This is consistent with
how we load enemies in EnemyGroupManager, and means one less file for
modders to worry about.
Merge pull request #1072 from stefanbeller/master

CMakeLists: make compatible with clang3.4; repair travis build
Update Japanese engine translation.
Merge pull request #1073 from Paul-Wortmann/master

Update Japanese engine translation.
Merge pull request #1066 from dorkster/fileparser

FileParser improvments
Create FindSDL2*.cmake files; Remove PkgConfig usage
Merge pull request #1075 from dorkster/cmake

Create FindSDL2*.cmake files; Remove PkgConfig usage
Rename SDLRenderDevice to SDLSoftwareRenderDevice
Add command-line flags to README.engine
Merge pull request #1076 from dorkster/renderer

 Rename SDLRenderDevice to SDLRenderDeviceSW
Don't floor() values that we cast to int

Doing so was a pointless step, since casting floats to ints implicitly
"floors" them.
Merge pull request #1078 from dorkster/fixes

Don't floor() values that we cast to int
Fix problems building with CodeBlocks/MinGW

- Fix searching for SDL2main
- Include cstring in MapCollision.cpp for memset()
- Include stdio.h in RenderDevice.cpp for fprintf()
Merge pull request #1080 from dorkster/windows

Fix problems building with CodeBlocks/MinGW
Move Image-specific functions from RenderDevice to Image class
Don't use "Surface" in RenderDevice function names

The following changes have been made:
Image::scaleSurface() -> Image::resize()
RenderDevice::loadGraphicSurface() -> RenderDevice::loadImage()
RenderDevice::createAlphaSurface() -> RenderDevice::createImage()
Rename Renderable's "sprite" variable to "image"
Merge pull request #1081 from dorkster/renderdevice

More RenderDevice fixes