Prefix alert type and alert position with EH*

[tciuro]

To avoid conflicts, I propose the following:

typedef enum : NSUInteger {
    EHPlainAlertError,
    EHPlainAlertSuccess,
    EHPlainAlertInfo,
    EHPlainAlertPanic,
    EHPlainAlertUnknown
} EHPlainAlertType;

typedef enum : NSUInteger {
    EHPlainAlertPositionBottom = 0,
    EHPlainAlertPositionTop
} EHPlainAlertPosition;