Changes for 8.1.0_RC2 (#5387)

* Fix dependency formatting in meta.yaml

* Pin gsl, update docs

* Revert pin

* Pin gsl to 2.6

* Add 8.1.0_RC1 as separate code entry

* Update the urls for 8.0 entry

* Turn on python bindings to be installed during build

* Add back kakadu build

recipe/build.sh

 mkdir build
 cd build
 export ISISROOT=$PWD
-cmake -GNinja -DJP2KFLAG=ON -Dpybindings=OFF -DKAKADU_INCLUDE_DIR=/isisData/kakadu -DbuildTests=OFF -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=$PREFIX ../isis
+cmake -GNinja -DJP2KFLAG=ON -Dpybindings=ON -DKAKADU_INCLUDE_DIR=/isisData/kakadu -DbuildTests=OFF -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=$PREFIX ../isis
 ninja install