RF: Widespread refactorings

With the aim of making the fsl/win-pytreatxrepository independent of any specific pytreat.

Pandas talk migrated to applications/pandas/.

fslpy practical migrated to applications/fsply/.

Python introduction talk migrated to getting_started/00_overview

advanced_programming/modules_and_packages.md

@@ -14,7 +14,7 @@ understandable manner.
 
 For this practical we have prepared a handful of example files - you can find
 them alongside this notebook file, in a directory called
-`02_modules_and_packages/`.
+`modules_and_packages/`.
 
 
 ## Contents
@@ -33,7 +33,7 @@ them alongside this notebook file, in a directory called
 
 ```
 import os
-os.chdir('02_modules_and_packages')
+os.chdir('modules_and_packages')
 ```
 
 <a class="anchor" id="what-is-a-module"></a>
@@ -41,7 +41,7 @@ os.chdir('02_modules_and_packages')
 
 
 Any file ending with `.py` is considered to be a module in Python. Take a look
-at `02_modules_and_packages/numfuncs.py` - either open it in your editor, or
+at `modules_and_packages/numfuncs.py` - either open it in your editor, or
 run this code block:
 
 
@@ -256,7 +256,7 @@ fact, there no difference between a _module_ and a _script_ - any `.py` file
 can be executed as a script, or imported as a module, or both.
 
 
-Have a look at the file `02_modules_and_packages/module_and_script.py`:
+Have a look at the file `modules_and_packages/module_and_script.py`:
 
 
 ```
@@ -272,7 +272,7 @@ that allows you to add code to a file that is _only executed when the module is
 called as a script_. Try it in a terminal now:
 
 
-> `python 02_modules_and_packages/module_and_script.py`
+> `python modules_and_packages/module_and_script.py`
 
 
 But if we `import` this module from another file, or from an interactive
@@ -351,7 +351,7 @@ from knowing that it is needed. But you can use `__init__.py` to perform some
 package-specific initialisation, and/or to customise the package's namespace.
 
 
-As an example, take a look the `02_modules_and_packages/fsleyes/__init__.py`
+As an example, take a look the `modules_and_packages/fsleyes/__init__.py`
 file in our mock FSLeyes package. We have imported the `fsleyes_main` function
 from the `fsleyes.main` module, making it available at the package level. So
 instead of importing the `fsleyes.main` module, we could instead just import