[#2,refactor][s]: remove funky layout (masonry) and have simple row layout for extensions.

* removes dep on isotope library (so we can remove from code)
* TODO: reinstate filtering properly
[#8,data][m]: first-pass working script to get master list and generate jekyll pages.
[theme/extension][xs]: fix image.
[#8,data][s]: automated build of jekyll pages using new script based on selected extensions in master sheet..