Add coding guidelines

CODING_STYLE

+KAlarmCal coding style
+======================
+
+KAlarmCal code should adhere to the following stylistic rules.
+
+SPACING
+
+- No tabs.
+- Indent with 4 spaces.
+- No spaces inside round or square brackets.
+- No space between a function name and the bracket following.
+- Place '*' and '&' immediately after the type in declarations, followed by a
+  space, e.g. "const QString& from", "char* str".
+- Normally two spaces on each side of "&&" and "||" in "if"/"while"/"for"
+  statements.
+- Indent "case" within "switch" statements.
+
+BRACES
+
+- Opening brace on a new line.
+- No braces are used when only a single statement follows 'if', 'for' etc.
+
+SPLITTING LINES
+
+- There is in general no need to split lines less than 120 characters. Beyond
+  that length, it's at the coder's discretion.
+- Conditional statements occupying line lengths less than 120 characters may be
+  split for clarity.
+- Long "for" statements should be split before each clause at least.
+- If a function call or declaration has to be split over more than one line,
+  indent to after the opening bracket if possible.
+- If splitting lines containing expressions, always split BEFORE an operator
+  ("+", "-", "&&" etc.) so that the operator starts the next continuation line.
+- In split conditional expressions, position the leading "&&" or "||" before
+  its enclosing bracket, so that the following expression aligns after the
+  opening bracket.
+
+NAMING
+
+- Classes, enums, functions and variable names are in camel case (i.e.
+  separate multiple words by upper-casing each word after the first). Only
+  use underscores for special purposes.
+- Classes and enum names start with an upper case letter.
+- Function and variable names start with a lower case letter.
+- Enum values are either all upper case with words separated by underscores, or
+  camel case starting with an upper case letter.
+- Constants are all upper case, with words separated by underscores.
+- Class member variable names start with "m" followed by a upper case letter.
+
+EXAMPLE
+
+Animal ZooCage::releaseAnimal(const QString& name, Species species,
+                              int arrivalNumber) const
+{
+    if (!name.isEmpty()
+    &&  (arrivalNumber > mMinimumSpeciesCount  &&  arrivalNumber < mMaximumSpeciesCount)
+      || !arrivalNumber)
+    {
+        mLastReleased = Animal(species, name, arrivalNumber);
+        return mAnimals[name][arrivalNumber];
+    }
+    if (name.isEmpty()  ||  mUnclassifiedAnimals.contains(name))
+        return mUnclassifiedAnimalTypes[species];
+    return Animal();
+}