Fixed typos, added strings for Of Peace of Mind

This updated just fixes some typos and includes the strings for Seneca's Of Peace of Mind but they're not accessible yet.

Typos and reordered menu

Fixed a typo in Epictetus' discourses and reordered Seneca's menu a bit.

Seneca Of Leisure

This version adds Seneca's Of Leisure and a quote by Zeno found within Seneca's piece.

Typo

Fixes typo in discourses.

Typo

Fixed a typo in discourses.

Typo

Fixed a typo in the discourses.

Typo

Small update to fix a typo in the discourses of Epictetus.

Formatting improvements

Gone through the strings.xml file to improve the formatting of texts.

Meditations edit

I removed the places where the first few books of Meditations were written. The placing of those lines is unclear so removed them altogether.

On the Happy Life

Added On the Happy Life by Seneca in this release and fixed a handful of typos too.