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.
Added documentation wiki link to web page
Reinstated --ffmpeg-<type>-opts

Reinstated --ffmpeg-<type>-opts to specify custom output options (e.g.,
filters) for ffmpeg re-muxing.  Pattern is:

ffmpeg -i infile -vcodec [vparams] -acodec [aparams] [ffmpeg-<type>-opts] -y outfile
Revamped recording modes

Default TV modes now set to flashvhigh and below. Introduced shortcuts
"good" and "better" to accompany "best". The default setting is
"better", with synonym "default".  Use "best" for HD programmes,
use "good" to revert to previous behaviour with "flashhigh" as
highest TV recording quality.

Default radio modes set to flashaachigh and below + wma.  Introduced
shortcuts "good" and "better" (with synonym "default) to accompany
"best". The "good", "better" and "best" shortcuts all result in the same
modes being used for radio programmes.  This retains existing behaviour,
where the best available recording quality is always used for radio
programmes. The Web PVR default "Recording Modes" value is now "default".

TV mode shortcuts

good    : flashhigh,flashstd,flashnormal,flashlow
better  : flashvhigh + <good>
best    : flashhd + <better>
default : synonym for 'better'
flash   : same as 'default'
rtmp    : same as 'default'

Live TV mode shortcuts: Same as above

Radio mode shortcuts

good     : flashaachigh,flashaacstd,flashaudio,flashaaclow,wma
better   : same as 'good'
best     : same as 'good'
default  : synonym for 'better'
flash    : flashaachigh,flashaacstd,flashaudio,flashaaclow
rtmp     : same as 'flash'
flashaac : flashaachigh,flashaacstd,flashaaclow

Live Radio mode shortcuts: Same as above
fixed --tag-cnid description
update radio urls

urls for radio schedules are now all prefixed with radio,
e.g. manchester/programmes/schedules is now radiomanchester/programmes/schedules
Fixes for channel schedules