plowprobe: comment fix

Plowprobe has its own section in configuration file.
Bug introduced in revision d9e346472ba66ed30f269214cd997da6de3c67d7

<diff>
-                process_configfile_module_options 'Plowdown' "$MODULE" PROBE
+                process_configfile_module_options '[Pp]lowprobe' "$MODULE" PROBE
</diff>
plowprobe: fix unwanted debug message

When --follow is disabled:

<code>
$ plowprobe -v3 http://thefile.me/sjs56qwu7dwa
dbg: Skip: 'http://thefile.me/sjs56qwu7dwa' (in http://thefile.me/sjs56qwu7dwa) doesn't seem to be a link
Skip: no module for URL (http://thefile.me/)
</code>

debug message must not be written in that case.
docs: prefer "verbosity level" to "verbose level"
multiup.org (list): fix

The "continue button" page seems to be remembered server side and not in cookies (PHPSESSID) anymore.
download.sh, probe.sh: cosmetics, drop useless double quotes in simple variable assignment
download.sh, core.sh: use string concatenation notation

This requires Bash 3.1+
upstore: minor cosmetics
gamefront (download, probe): fix detection of deleted files
uptobox (premium download): fix

Fixes issue 1132.
multiup_org (list): deal with queued upload

In that case, returns $ERR_LINK_TEMP_UNAVAILABLE instead of $ERR_FATAL.
upstore: add premium account support
oboom (upload): fix folder ID parse

Fixes issue 1135.
oboom (upload): fix folder ID parse, take two

Try to parse folder ID before creating one.
core.sh cosmetics (comment fix, +=)
plowprobe: avoid two subshells
plowdown, plowprobe: use mapfile (Bash4 builtin)

Useful for reading lines into an array.
uptobox (download): fix wrong dead link detection
billionuploads (download): fix base64 decode

Mac compatibility
base64 checks + compatibility fix
plowdown, plowup: test for POSIX mode

Plowshare can't work in bash POSIX mode because lots of features are disabled.