Move Manual_version to Intro

It should not be its own chapter. The intro seems to be the right place for it.

doc/src/Intro.txt

@@ -17,6 +17,7 @@ These pages provide a brief introduction to LAMMPS.
 .. toctree::
 
    Intro_overview
+   Manual_version
    Intro_features
    Intro_nonfeatures
    Intro_opensource

doc/src/Manual.txt

@@ -71,7 +71,6 @@ every LAMMPS command.
    :name: userdoc
    :includehidden:
 
-   Manual_version
    Intro
    Install
    Build

doc/src/Manual_version.txt

@@ -7,7 +7,7 @@ Documentation"_ld - "LAMMPS Commands"_lc :c
 
 :line
 
-What does a LAMMPS version mean: :h3
+What does a LAMMPS version mean :h3
 
 The LAMMPS "version" is the date when it was released, such as 1 May
 2014. LAMMPS is updated continuously.  Whenever we fix a bug or add a

doc/src/lammps.book

 #HTMLDOC 1.8.28
 -t pdf14 -f "../Manual.pdf" --book --toclevels 4 --no-numbered --toctitle "Table of Contents" --title --textcolor #000000 --linkcolor #0000ff --linkstyle plain --bodycolor #ffffff --size Universal --left 1.00in --right 0.50in --top 0.50in --bottom 0.50in --header .t. --header1 ... --footer ..1 --nup 1 --tocheader .t. --tocfooter ..i --portrait --color --no-pscommands --no-xrxcomments --compression=9 --jpeg=0 --fontsize 11.0 --fontspacing 1.2 --headingfont Sans --bodyfont Serif --headfootsize 11.0 --headfootfont Sans-Bold --charset iso-8859-15 --links --embedfonts --pagemode document --pagelayout single --firstpage c1 --pageeffect none --pageduration 10 --effectduration 1.0 --no-encryption --permissions all  --owner-password ""  --user-password "" --browserwidth 680 --no-strict --no-overflow
 Manual.html
-Manual_version.html
 Intro.html
 Intro_overview.html
+Manual_version.html
 Intro_features.html
 Intro_nonfeatures.html
 Intro_opensource.html