Quote command strings in verbose output

Quoted command strings in verbose output can now be cut and pasted to
command prompt (cut and paste may not work for some commands in Windows).
Revert "Added --ffmpeg-<type>-opts to man page"

This reverts commit 7ff95ce42a0fadb112f7e7d9c8935f8bba42e2d6.
Removed --ffmpeg-<type>-opts

This feature isn't very useful with re-muxing in get_iplayer.  Keep it
simple and remove until someone comes up with use cases.
Replace leading ellipsis when sanitising output file/directory names

Avoids creation of invisible files/directories on Linux/OSX for programmes
like "…Sings the Beatles"
Use --rtmpdump in preference to --flvstreamer

Internal references to flvstreamer changed to rtmpdump and --rtmpdump
is now preferred option to specify location of binary.  --flvstreamer
is retained as synonym for --rtmpdump and flvstreamer options is still
supported in options files.
Restore lines accidentally commented out
Don't use unnecessary character entities in XML metadata files

Character entities (e.g., &pound) in XML metadata files cause problems
in post-processing because the entities are usually undefined.  Restrict
encoding to minimal character sets: &<>"' in attributes, &<> in element
text.
Make XML entity encoding uniform

Now encodes &<>"' in both attributes and element text
Make script more portable with usr/bin/env

http://www.cyberciti.biz/tips/finding-bash-perl-python-portably-using-env.html

This allows get_iplayer to "just work" with perlbrew installations

http://perlbrew.pl/

While remaining back-compat with any traditional / standard installation / setup.
Removed extraneous line of code
Minor README edits
Added system plugin location for Windows
Added optional version string

$version_text can be set by installers to override formatted $version
printed in copyright notice (get_iplayer -V).  $VERSION_TEXT added to
web per added for same purpose.
Web PVR: change shebang to /usr/bin/env
Added web pvr logo image
More readme edits
Minor readme edit
Updated SWF player URL
Replaced links to linuxcentre.net

Web PVR logo image now loaded from infradead.org.
Added avconv support

avconv now used by default if present in $PATH. This will generally
only be the case for Debian/Ubuntu systems.  Also added --avconv as
synonym for --ffmpeg.