Base documentation - minor revisions

Many revisions on the base.rst. Formated and added new examples, inserted some returned types, etc.
Corrections on base.rst previous commit

Removed type annotation of some functions
Corrected identation and comments
better handling of empty file in readdlm.
fixes #6898
add complex log1p (fix #3141)
doc: typo in output
faster and more compact serialization of symbols and strings
Set function performance: build up sets instead of copying and deleting
Merge pull request #6904 from stevengj/log1p

add complex log1p
Merge pull request #6905 from simonbyrne/patch-1

doc: typo in output
Merge pull request #6902 from tanmaykm/readcsv

better handling of empty file in readdlm.
tab substitution of LaTeX symbols in REPL (fixes #6340)
make deserialization backwards compatible (allow reading old data)

make serializing strings even faster
Merge branch 'master' of github.com:JuliaLang/julia
remove duplicate LaTeX symbols (font variations) ... fortunately, it looks like the most reasonable choice is listed first in the unicode.xml file
add \sqrt and \cbrt substitutions
fix #6909
add missing \mars and \female substitutions, for consistency as pointed out by @mbauman
Merge pull request #6911 from stevengj/latex

RFC: tab substitution of LaTeX symbols in REPL
Faster implementation of var across dimensions