Added documentation for "MODE_ONECLICK" and "MODE_PAINT_WITH_PREVIEW",
which were added to Tux Paint magic API 0x00000003 in Tux Paint 0.9.22)
to Tux Paint magic tool development docs.
Magic tool documentation now split into separate files, and referenced
(as a directory) from README, so that users can find docs to any additional
tools (ones not included by default with Tux Paint) that are installed.
Added new --datadir option, to separate path to brushes/stamps/etc. from that of saved files.
Improved docs on where savedir default is.
Made sure --help, man tuxpaint, and OPTIONS docs all covered all command-line options.
Noted SDL_Pango makes locale-specific fonts unnecessary.
Added "--plugindocprefix" option to tp-magic-config, for where docs should go.
Improved plugin API documentation.
Improved layout of man pages a little.
Added --pluginprefix and --dataprefix to tp-magic-config script.
Started a glossary section in API documentation.
Added Table of Contents to API documentation.
Added a manpage for tp-magic-config script.
