Clean up the HISTIGNORE Bash variable

[xty]

The following passage from the Bash Reference Manual provides justification for the proposed changes:

HISTIGNORE subsumes the function of HISTCONTROL. A pattern of ‘&’ is identical to ignoredups, and a pattern of ‘[ ]*’ is identical to ignorespace. Combining these two patterns, separating them with a colon, provides the functionality of ignoreboth.

The relevant section as it stands:

dotfiles/.bash_profile

Lines 57 to 63 in 8936892

	export HISTCONTROL="ignoredups" # no duplicate entries, but keep space-prefixed commands
	export HISTSIZE=100000 # big big history (default is 500)
	export HISTFILESIZE=$HISTSIZE # big big history
	type shopt &> /dev/null && shopt -s histappend # append to history, don't overwrite it
	# Don't record some commands
	export HISTIGNORE="&:[ ]*:exit:ls:bg:fg:history:clear"

Specifically, this PR is aimed at ironing out these kinks:

1. Having both & in HISTIGNORE and ignoredups in HISTCONTROL is redundant.
2. Assuming the intention was to preserve commands with a leading space (as indicated by the comment in Line 57), the inclusion of [ ]* in HISTIGNORE would be self-defeating.