Couple of small modifications for Android

This checkin contains two small changes:
- The first is simply to add to Android.mk the two new files that we created as part
  of our refactoring of the code for filter chains in Readium SDK. Two new files were
  created and now they are part of the Android build as well.
- Second, in order to let Android compile, GCC does not recognize the "ios::seekdir"
  enumeration the same way that clang does. Therefore, we have to use
  "std::ios::beg" instead of "std::ios::seeker::beg" for GCC. I already checked that
  clang compiles with this change too.
Merge the recent develop changes into feature/AndroidByteRangeStream
Changes in Android to support font obfuscation

This change tackles the fact that the Launchers need to call
Package::GetFilterChainByteStream() in order to get a byte stream
that has ContentFilter objects hooked up to it. Without that call, you can
get a byte stream, but it does not have any ContentFilter and therefore
things like obfuscated fonts don't work. Notice, however, that this change
does not allow Android to make use of byte ranges yet.
Remove duplicate cpp file includes.
Small modifications to get the Android code to compile.
Prevent calling epub_sys_cache_flush on devices running Android.
Merge branch 'develop' into feature/AndroidByteRangeStream
Check if manifest item is null before attempting to use a filtered byte stream with it.
Use a relative path for obtaining the manifest item.
Temporarily rename JNI's package.cpp wrapper
To ease debugging with conflicting file names between that and SDK's package.cpp
Support for byte ranges in Readium SDK in Android

This checkin includes some changes that will allow Readium SDK to support
byte ranges in Android. In a nutshell, these changes add another native
method to the set of native methods associated with the Package class.
This new method will receive a range, and it will instantiate a
FilterChainByteStreamRange object based upon the request. Then, it
will use that FilterChainByteStreamRange to extract a range of bytes
from a given resource, and it will return those bytes inside a ByteBuffer.
Later, the EpubServer class will put that ByteBuffer inside a
ByteArrayInputStream, and it will pass that to the Nano HTTP Server,
in order to fulfill a request.
Fix up range implementation.
Refactor the byte stream range call into the input stream call. Create a non filter chain capable (raw) input stream. Buffer size can now be specified from above.
Improve raw input stream operations but error out for regular input stream (filter chain based ones for now). Add range byte reading support for both stream types.
Merge branch 'develop' into feature/AndroidByteRangeStream

Conflicts:
	ePub3/utilities/byte_buffer.cpp
Remove debug optim level
Add Package Resource helper class
Close resource stream after reading a range of bytes
Merge branch 'develop' into feature/AndroidByteRangeStream
somehow, std::ios::seekdir::beg sneaked in again!