Added file type and tabs documentation.

help/file-type.dhf

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+# File Type
+
+The language (or type) of a file is shown in the status bar between
+parentheses.  For example, the file type of this help document is "dhf".
+
+Diakonos can usually guess a file's language correctly.  To do so, it
+considers the filename and, if present, the "bang" line at the top of the
+file.  The bang line takes precedence over the filename.
+
+If Diakonos was wrong in its automatic determination of the file type, you can
+force it to assume a certain file type by pressing <Alt-Shift-T> and typing in
+the file type (e.g. java, ruby, html, xml, and so on).
+
+The configuration settings (available by pressing <F12>) which affect
+Diakonos' guessing are a language's filemask and bangmask settings.  These
+settings are regular expressions.  For example:
+
+lang.perl.filemask \.(?:pl|pm)$
+lang.perl.bangmask perl
+
+These configuration lines tell Diakonos to think a file is a Perl file if its
+extension is .pl or .pm, or if the bang line has the word "perl" in it.
+
+Tags: file files lang language languages programming type mode types modes

help/tabs.dhf

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+# Tabs
+
+## Changing the width of tab characters
+
+The width of a tab character depends on the language of the file.  To change
+the width for a specific language, change the tabsize setting for the
+language.  For example, to change the tabsize of Ruby files, open the
+configuration file by pressing <F12>, and look for a line like this:
+
+lang.ruby.tabsize 2
+
+Then change the number 2 to whatever number you desire, such as 4.
+
+## Indenting with tab characters instead of spaces
+
+By default, Diakonos indents with spaces.  To make it indent with tab
+characters instead, look for the ident settings for the language.  For
+example, to change the indentation of Ruby, add the following line to your
+configuration file (<F12>):
+
+lang.ruby.indent.using_tabs true
+
+Tags: tab tabs indent indenting indentation space spaces whitespace char character characters width size number