Add pipes to write pretty PowerShell #53

This commit introduces two pipes: `inlinePowerShell`,
`escapeDoubleQuotes`. The types when used together allows writing adding
clean and real PowerShell scripts as they are (without inlinining or
escaping them), removing the need to have hard-coded inlining/escaping.

It enables writing better PowerShell, makes it easier to maintain and
extend PowerShell scripts. Also allows writing more stable code with
less "unseen" bugs due to manual escaping/inlining. This commit
naturally reveals and fixes double quotes not being escaped in "Empty
trash bin" script.

This is solved by unifying the use of RunPowerShell function by all
scripts using PowerShell. The function inlines and escapes the scripts
as compile time to be send them to PowerShell.exe as an argument and
then invokes PowerShell.exe with generated ugly code.

docs/templating.md

@@ -79,3 +79,9 @@ A function can call other functions such as:
 - Pipes are provided and defined by the compiler and consumed by collection files.
 - Pipes can be combined with [parameter substitution](#parameter-substitution) and [with](#with).
 - ❗ Pipe names must be camelCase without any space or special characters.
+- **Existing pipes**
+  - `inlinePowerShell`: Converts a multi-lined PowerShell script to a single line.
+  - `escapeDoubleQuotes`: Escapes `"` characters to be used inside double quotes (`"`)
+- **Example usages**
+  - `{{ with $code }} echo "{{ . | inlinePowerShell }}" {{ end }}`
+  - `{{ with $code }} echo "{{ . | inlinePowerShell | escapeDoubleQuotes }}" {{ end }}`