libdeng2|Reader: Added a method to read a specific number of bytes

Added a method that is more convenient to use than reading a
FixedByteArray.
libdeng2|Reader|Write: Reading/writing fixed-size byte arrays

Added more convenient methods for reading and writing byte arrays of
preset size, which means the size itself won't be read/written, only
the bytes.
Cleanup|Savegame Tool: Unnecessary use of char[]

Block is already a "raw" buffer of bytes, so there is no need to
have another buffer just for access to the raw bytes.

Block also automatically zero-terminates the content (the byte
following its actual contents).

Block automatically expands when writing adjacent to its end so there
is no need to reserve size beforehand.
Cleanup|libcommon: Streaming bytes directly to a File

When streaming directly to a File via the IOStream interface, one
does not need to use FixedByteArray as the operation will replace the
entire contents of the file. Files have built-in metadata about
their size, so size won't be included in the written data as with
Writer.
Cleanup|libcommon: Accessing pointer-based byte arrays

de::ByteRefArray is the appropriate array class to use for referencing
an existing pointer-based array of bytes with a known size.
Cleanup|Savegame Tool: Take advantage of Qt methods

Block is a QByteArray.
Fixed|OS X|Savegame Tool: Build config and deployment

Added the tool to the app bundling script and fixed the build settings
to produce the right kind of executable. Also added missing dependency
to libdeng1 (needed by Unix version of lzss).
Fixed|Savegame Tool: Build issues (extra qualifiers)
Fixed|Savegame Tool: Missing virtual destructor

Classes with virtual methods should have a virtual destructor.