'pad.zero' adds zeroes to the front of character strings (usually
digit strings) if they are needed to make the strings be of a
particular length.  Usually this is useful to create filenames
that will sort in a particular order in a Windows program.
E.g., 'x1', 'x10', 'x2, 'x3' will sort in exactly this order
in many Windows programs, but 'pad.zero' can be used (along
with other code) to convert these strings to 'x01', 'x10',
'x02', 'x03'.
ARGUMENTS:
'x' = a character vector, usually a vector of digit strings
'N.char' = number of characters in every output string - defaults
to the number of characters in the longest string in 'x'
'lead.char' = optional initial character to precede the zeroes.

palette.default is a vector of color names that represent JM's  current preferred plotting colors.

'path.curr' has no effect if R is not running on one of JM's computers.  The only reason for using the 'path.curr' function is that JM works on several different computers with different directory structures.  By using the 'path.curr' function, JM is able to write code that finds corresponding files on the different computers.  If the user is not working on one of JM's computers, then the 'path.curr' function will output the 'filepath' argument without any changes to it.  

Currently (8/21/2013), there are 3 JM computers:  X220, UHouse and JC's ThinkPad.

In the case where R is running on one of JM's computers, 'path.curr' takes a path+filename specification and returns the full path + filename including the drive letter, e.g., "/aa/bb.rda" is returned as "e:/aa/bb.rda" on the X220 computer and as "b:/ab/john/aa/bb.rda" on Dad's computer.  If the 'filepath' argument has the form 'objectName' (no slash) or 'dir/dir/objectName' (no starting slash), then 'path.curr' has no effect (it returns 'filename' unchanged).  In other words, object names or relative paths + object names are unchanged, but an absolute path starting at the root directory is changed to conform to JM's current computer.  

ARGUMENT:

'filepath' = a path + filename specification.   
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