separate indirect calls and calling convention sections

a571701911408d47e2f147f9dff99c461153a328@julia
Updates first few sections of the manual

Mainly affects the two sections about primitive numbers and elementary operations.

[x] Adds videos from MIT tutorial to Getting Started
[x] Consolidates and tabulates primitive types, operators and elementary functions rather than having them in list form
[x] Adds sections about overflow behavior of integers and signed zero float values
[x] Expands documentation for eps
[x] Documents `\` and `^` operators
[x] Minor formatting changes and spelling and grammatical corrections.

JuliaLang/julia@016823a8eaee8521067bf2554312beb32daa4bf4