[SPARK-9558][DOCS]Update docs to follow the increase of memory defaults.

Now the memory defaults of master and slave in Standalone mode and History Server is 1g, not 512m. So let's update docs.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #7896 from sarutak/update-doc-for-daemon-memory and squashes the following commits:

a77626c [Kousuke Saruta] Fix docs to follow the update of increase of memory defaults