dev-libs/swaylock: various fixes

dev-libs/swaylock: various fixes

 - Use ${PN} wherever possible;

 - Fix use flag order in IUSE;

 - Remove bash-completion use flag: bash completions should be always
   installed (see [1]);

 - Rename use flag: doc -> man (doc is a global use flag used to install
   additional documentation that most users does not want);

 - Fix order of (R)DEPEND;

 - Remove required use gdk-pixbuf[jpeg]: the jpeg use flag is not
   required to be enabled. If the user wants support for JPEG images, he
   can manually enable it in gdk-pixbuf;

 - Move scdoc and wayland-protocols deps to BDEPEND (required only when
   building);

 - Fix dependency blocks: an user may install <=sway-1.0_beta2 with the
   swaylock use flag disabled and then install the swaylock package;

 - Add -Dwerror=false to meson args.

In metadata.xml:

 - Add upstream infos;

 - Improve longdescription;

 - Add myself as maintainer.

[1] www.gentoo.org/support/news-items/2014-11-25-bash-completion-2_1-r90.html

Package-Manager: Portage-2.3.59, Repoman-2.3.12
Signed-off-by: Niccolò Scatena <speedjack95@gmail.com>
Signed-off-by: Aaron Bauman <bman@gentoo.org>