Misc. typos

+ some are doxy others are just comment code.  
+ some minor whitespace and grammatical tweaks. 
+ app/SCL/* typos have also been submitted upstream (https://github.com/stepcode/stepcode/pull/366). So it's ok to merge them in to master.

src/Mod/TechDraw/App/DrawViewSpreadsheet.cpp

@@ -120,7 +120,7 @@ App::DocumentObjectExecReturn *DrawViewSpreadsheet::execute(void)
 
 std::vector<std::string> DrawViewSpreadsheet::getAvailColumns(void)
 {
-    // build a list of available colums: A, B, C, ... AA, AB, ... ZY, ZZ.
+    // build a list of available columns: A, B, C, ... AA, AB, ... ZY, ZZ.
     std::string alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
     std::vector<std::string> availcolumns;
     for (int i=0; i<26; ++i) {