[e.cash] Fix typos, broken links, and cap-consistency on all pages

Summary: quick fixes as described above as well as requested changes to copy.

Test Plan: review copy and links on every page

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: johnkuney, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D18708