MSF started to the extended API with window enum

Decided to kick off a new extended API extension with mubix and
kernelsmith to include some more advanced enumeration stuff. The goal of
this extension is to take stuff that wouldn't be part of the std api but
is rather useful for enumeration of a target once meterpreter has been
established.

This commit kicks things off with enumeration of top level windows on the
current desktop.
Add service_enum to the ext_server_extapi extension

This commit adds the ability to enumerate services on the target machine,
showing the PID, the service name, the display name and an indication of
the service's ability to interact with the desktop.

Some other small code tidies were done too.
Add service_query to ext_server_extapi

Once the user has queried the list of services they can now use the
`service_query` function to get more detail about a specific service.
Improve extapi ruby structure, add bins

The extapi project will get bigger over time so this change allows for the code to get
bigger without becoming a headache before it starts.

Added binaries to this commit as well.
Add support for child window enumeration

Children of windows can now be enumerated via the -p parameter, which
specifies the handle of the parent window to enumerate.

There is also a -u parameter which includes unknown/untitled windows
in the result set.
Add the start of clipboard support

This commit adds support for getting text-based information from the
victim's clipboard and for setting text-based data to the victim's
clipboard. Early days, with much wiggle room left for extra fun
functionality.
Add CF_HDROP file support to the clipboard

`clipboard_get_data` has been changed so that raw text is supported and file listings are supported.

If files are on the clipboard, those files and folders are listed when this command is run. To download the files, pass in the `-d` option.
Add size (bytes) of the files on the clipboard

Output of the `clipboard_get_data` call now includes the size
of each file in bytes.
Add support for CF_DIB clipboard formats

Image data copied to the clipboard, such as a screenshot, is converted to a JPEG using GDI+, and downloaded to the local loot folder.

This feature doesn't work with W2K as a result, but that doesn't really bother me. The code is simpler and much smaller as a result and doesn't require the inclusion of the jpeg library code.
Tidy up of extapi code, new bins

* Rename methods to remove redundancy.
* Update bins to freshly compiled version.
* Use the Rex Table functionality instead of custom look.
* Use the `usage` feature of the Arguments class for help.
Add support for optional image downloading

Without -d, `CF_DIB` types will just show image dimensions. Running
with -d will result in the image being looted.
Updated help, removed binaries
Add byte xori mipsbe encoder
Stop auto preview, code clean

Removed the auto preview of captured images from the clipboard.

Removed parens from calls to print_line.
Remove shebang, code tidy, as per @jlee-r7's gripes
Last lot of shebangs removed
Start clipboard monitor functionality

Added the basics of the clipboard monitor functionality with usage
messages and stuff like that. Lots more to do.
Merge branch 'upstream/master' into ext_server_extapi
Add the binaries from the meterpreter repo

Given this is a new extension, building bins and including them in this
PR can't cause any issues regarding lost functionality (like it can
with existing bins).

Adding to this PR so that it's easier to test and land.
EXTAPI Test Module